Processing tool, method of producing processing tool, processing method and processing apparatus

ABSTRACT

A processing tool is used to carry out a fixed-abrasive grinding process on a surface of a silicon work-piece. The processing tool includes abrasive grains made up silica grains. A primary average grain size of the silica grains is desirably 0.8 nm to 10 μm.

[0001] This application claims the benefit of Japanese PatentApplications No.11-237467 filed Aug. 24, 1999, No.11-260799 filed Sep.14, 1999, No.11-278608 filed Sep. 30, 1999 and No.11-206355 filed Oct.28, 1999, in the Japanese Patent Office, the disclosures of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to processing tools,methods of producing processing tools, processing methods and processingapparatuses, and more particularly to a processing tool which is used togrind a work-piece made of silicon or the like, a method of producingsuch a processing tool, a processing method for processing a peripheralpart of a work-piece, and a processing apparatus

[0004] 2. Description of the Related Art

[0005] Conventionally, in a finishing process of a silicon wafer, apolishing process uses colloidal silica as the slurry and a flexiblepolishing cloth as the polishing tool. However, since the polishingprocess uses the slurry, there are problems in that the processingenvironment is harsh, the waste water must be processed, the runningcost of the processing system is high, the processing efficiency is low,and the shaping accuracy (flatness) is poor. For this reason, there aredemands to carry out the finishing process of the silicon wafer by afixed-abrasive machining apparatus, that is, by use of a fixed-abrasivegrinding tool such as a grindstone and a polishing film, and varioustools therefor have been proposed.

[0006] As conventional techniques which utilize the mechano-chemicalreaction between barium carbonate and silicon, there is a firstconventional technique proposed in a Japanese Laid-Open PatentApplication 5-285844, a second conventional technique proposed in aJapanese Laid-Open Patent Application No.5-285847, and a thirdconventional technique proposed in a Japanese Laid-Open PatentApplication No.10-329032.

[0007] According to the first through third conventional techniques, thegrindstone is formed by abrasive grains which are made of bariumcarbonate. By utilizing the mechano-chemical reaction that occursbetween the abrasive grains and silicon, a processed surface having ahigh quality is obtained, similarly to a case where a loose-abrasivepolishing process is carried out, such that no residual damage remainsafter the processing. In other words, it is possible, by using thebarium carbonate for the abrasive grains, to replace the conventionalpolishing process by the grinding process.

[0008] On the other hand, silica generates a mechano-chemical reactionwith respect to silicon. In addition, since the constituent elements ofsilica are silicon and oxygen, silica will not form on the silicon aresidual contamination resulting from the mechano-chemical reactionbetween the silica and the silicon. Furthermore, since the mechanicalhardness of silica is higher than that of barium carbonate, it ispossible to realize a high removing efficiency while maintaining thehigh accuracy of the processed surface.

[0009] For example, in a fourth conventional technique proposed in aJapanese Laid-Open Patent Application No.8-276366, a resin bondedgrindstone is produced by using silica as the aggregate. In fifth, sixthand seventh conventional techniques respectively proposed in JapaneseLaid-Open Patent Applications No.5-285843, No.10-166259 and No.9-47969,the grindstone for grinding a sapphire substrate uses silica for theabrasive grains.

[0010] According to the fourth conventional technique, silica is notused for the abrasive grains, but is used for the aggregate, so as toimprove the dispersibility of the abrasive grains and improve theadjustment of the specific gravity of the binder.

[0011] According to the fifth and sixth conventional techniques, thegrindstone for grinding sapphire is formed by using silica which ismechanically softer than sapphire. A high-quality grinding of sapphireis realized by utilizing the mechano-chemical reaction at a point ofcontact between the abrasive grains and the sapphire.

[0012] According to the seventh conventional technique, ultra-finesilica or silicon oxide powder having a grain diameter of several tensof nm or less is used as the abrasive grains. A silicon wafer or thelike is mirror finished with a high accuracy without loading, by use ofthe grindstone which is formed at a predetermined porosity. It is,however, not the main object of the seventh conventional technique togenerate the mechano-chemical reaction by the use of the silica abrasivegrains.

[0013] When barium carbonate is used for the abrasive grains as in thecase of the first through third conventional techniques, themechano-chemical reaction between the barium carbonate and the siliconcauses a compound thereof to be generated on the silicon as residualcontamination. The compound is made up of barium, silicon and oxygen.Hence, the generated contamination deteriorates the quality of theprocessed surface, and it is necessary to carry out a cleaning processas an after-process. Moreover, the barium carbonate has a mechanicalhardness lower than that of the silicon and is easier to process thebarium carbonate with a high accuracy, but as a consequence, theremoving efficiency is too low for use during the production process.

[0014] On the other hand, as in the case of the fourth conventionaltechnique, silica is generally used as the aggregate, so as to improvethe dispersibility of the abrasive grains and improve the adjustment ofthe specific gravity of the binder, when carrying out the process usingthe resin bonded grindstone. In the fifth and sixth conventionaltechniques, silica is used as the abrasive grains for polishingsapphire, but no consideration is given on the use of silica as theabrasive grains for polishing a silicon wafer. Further, since theseventh conventional technique uses the silica powder having a graindiameter of several tens of nm or less, it is difficult to realize ahigh removing efficiency.

SUMMARY OF THE INVENTION

[0015] Accordingly, it is a general object of the present invention toprovide a novel and useful processing tool, method of producingprocessing tool, processing method and processing apparatus, in whichthe problems described above are eliminated.

[0016] Another and more specific object of the present invention is toprovide a processing tool, method of producing processing tool,processing method and processing apparatus, which use silica abrasivegrains to generate a mechano-chemical reaction with respect to siliconbut prevents residual contamination from remaining on the silicon due tothe mechano-chemical reaction.

[0017] Still another object of the present invention is to provide aprocessing tool for carrying out a fixed-abrasive grinding process on asurface of a silicon work-piece, comprising abrasive grains made upsilica grains. According to the processing tool of the presentinvention, it is possible to utilize the mechano-chemical reactiongenerated by the silica grains on the silicon work-piece, and realize ahigh removing efficiency while maintaining a high quality of theprocessed surface.

[0018] A further object of the present invention is to provide a methodof producing a processing tool having abrasive grains for carrying out afixed-abrasive grinding process on a surface of a silicon work-piece,comprising the step of (a) mixing a binder and silica grains to form amixture, and (b) forming the mixture into the abrasive grains of theprocessing tool. According to the method of the present invention, it ispossible to produce a processing tool which utilizes themechano-chemical reaction generated by the silica grains on the siliconwork-piece, to realize a high removing efficiency while maintaining ahigh quality of the processed surface.

[0019] Another object of the present invention is to provide aprocessing method for carrying out a fixed-abrasive grinding process ona surface of a silicon work-piece, comprising the steps of (a)positioning the silicon work-piece relative to a processing tool havingabrasive grains made up silica grains, and (b) processing the surface ofthe silicon work-piece by the abrasive grains of the processing tool.According to the processing method of the present invention, it ispossible to utilize the mechano-chemical reaction generated by thesilica grains on the silicon work-piece, to realize a high removingefficiency while maintaining a high quality of the processed surface.

[0020] Still another object of the present invention is to provide aprocessing method for carrying out a process on a disk-shaped ordonut-shaped work-piece, comprising the steps of (a) grinding an outerperipheral surface of the work-piece by a grindstone, and (b) polishingcutout part on the outer peripheral surface of the work-piece and/or aninner peripheral surface of the work-piece by a polishing film.According to the processing method of the present invention, it ispossible to stably and suitably process various kinds of surfaces of thework piece with a high efficiency, so as to obtain processed surfaceshaving a high quality, at a low running cost.

[0021] A further object of the present invention is to provide aprocessing apparatus for carrying out a process on a disk-shaped ordonut-shaped work-piece, comprising a grinding unit grinding an outerperipheral surface of the work-piece by a grindstone, a polishing unitpolishing cutout part on the outer peripheral surface of the work-pieceand/or an inner peripheral surface of the work-piece by a polishingfilm, and a transport unit transporting the work-piece at least betweenthe grinding unit and the polishing unit and positioning the work-piecein the grinding unit and the polishing unit. According to the processingapparatus of the present invention, it is possible to stably andsuitably process various kinds of surfaces of the work piece with a highefficiency, so as to obtain processed surfaces having a high quality, ata low running cost.

[0022] Other objects and further features of the present invention willbe apparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a diagram for explaining a second embodiment of aprocessing apparatus according to the present invention;

[0024]FIG. 2 is a diagram for explaining a third embodiment of theprocessing apparatus according to the present invention;

[0025]FIG. 3 is a diagram showing the general construction of a fifthembodiment of the processing apparatus according to the presentinvention;

[0026]FIG. 4 is a side view showing the shape of a grindstone;

[0027]FIG. 5 is a plan view showing a disk which is processed;

[0028]FIG. 6 is a cross sectional view showing a polishing film; and

[0029]FIG. 7 is a diagram showing the general construction of a sixthembodiment of the processing apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] A description will be given of a first embodiment of a method ofproducing processing tool according to the present invention. This firstembodiment of the method of producing processing tool produces a firstembodiment of a processing tool according to the present invention. Inthis embodiment, a grindstone of the processing tool uses silica whichgenerates a mechano-chemical reaction with respect to silicon.

[0031] In this embodiment of the method of producing the processingtool, this embodiment of the processing tool is produced by a mixingstep and a forming step. The mixing step mixes silica and a liquidresin, together with an additive such as a solid lubricant if necessary.The mixture is stirred, so as to obtain a binder resin (mixture) whichincludes silica abrasive grains.

[0032] Silica generates a mechano-chemical reaction with respect tosilicon. However, since the constituent elements of silica are siliconand oxygen, silica will not form on the silicon a residual contaminationresulting from the mechano-chemical reaction between the silica and thesilicon. Further, silica has a satisfactory mechanical hardness which ishigher than that of barium carbonate, such that a high removingefficiency can be realized while maintaining the surface quality of aprocessed surface high when the silica processing tool is used toprocess the surface of a work-piece.

[0033] In this case, the silica content in the abrasive grains is 10 to70 volume percent (%), and an average grain diameter of silica is 0.8 nmto 10 μm.

[0034] If the silica content in the abrasive grains is less than 10volume %, the silica abrasive grains do not generate the desiredreaction on silicon. On the other hand, if the silica content in theabrasive grains exceeds 70 volume %, the loading of the grindstoneoccurs, and the processing easily becomes unstable. In this latter case,the amount of binder also becomes insufficient, and there is apossibility that a desired tool strength required to process thework-piece is not be obtainable.

[0035] If the average grain diameter used for the grindstone of theprocessing tool is less than 0.8 nm, the mechanical action on thework-piece becomes too small, and a desired mechano-chemical reactioncannot be generated. On the other hand, if the average grain diameterused for the grindstone exceeds 10 μm, the mechanical action becomes toolarge, and there is a possibility of generating damage to the processingsurface of the work-piece, such as a silicon wafer surface.

[0036] On the other hand, the binder material is not limited to a resin,and various other materials such as ceramics, metals, silicate andmagnesia may be used depending on the object of the processing which isto be carried out by use of the processing tool. It is desirable thatthe binder material does not generate an endothermic reaction during theprocessing. For example, polymer materials such as phenol resins andpolyimide resins may be used for the binder material.

[0037] As described above, silica generates the mechano-chemicalreaction with respect to silicon. But it is necessary that a processingambient temperature is sufficiently high so that the chemical reactionof the mechano-chemical reaction occurs. If the binder is made of amaterial such as an acrylic resin which has a low melting point, thebinder will melt due to heat which is generated during the processcarried out with respect to the work-piece, and the endothermic reactiongenerated by the melting of the binder causes the processing ambienttemperature to decrease. Consequently, it would become impossible togenerate the mechano-chemical reaction at the decreased processingambient temperature.

[0038] Therefore, the use of ceramics, metals and polymer materials suchas phenol resins and polyimide resins as the binder prevents the binderfrom melting during the process carried out with respect to thework-piece, which would thereby cause the endothermic reaction that willdecrease the processing ambient temperature.

[0039] Of course, it is possible not to include the binder in themixture. In this case, the silica abrasive grains are mutually bonded bysiloxane bonding to form the processing tool.

[0040] If necessary, the additive is added to improve the strengthand/or lubrication of the processing tool. The additive is alsodesirably made of a material which does not generate an endothermicreaction during the processing, since the endothermic reaction woulddecrease the processing ambient temperature and thereby make itimpossible to generate the mechano-chemical reaction between silica andsilicon. For example, materials such as carbon and molybdenum disulfidemay be used for the additive. The use of such materials for the additiveensures generation of the mechano-chemical reaction, by preventing theadditive from melting and generating the endothermic reaction during theprocess which is carried out with respect to the work-piece.

[0041] The forming step is carried out after the mixing step ends. Theforming step forms the grindstone by employing an abrasive machiningmethod which suits the binder used.

[0042] When making a resin bonded grindstone or a vitrified grindstone,the mixture which is obtained by the mixing step is subjected to apressurized baking and drying. Alternatively, a technique employing theelectrophoretic effect as taught in a Japanese Laid-Open PatentApplication No.2000-176842 may be employed. When making a metal bondedgrindstone, electrodeposition, hot pressing or the like is employed.Furthermore, when producing a film-shaped processing tool, a coatingstep is carried out prior to the forming step, so as to coat a binderresin (mixture) on a resin film. In this coating step, the mixture iscoated on a base material, that is, a resin film, which is made ofpolyethylene telephthalate, for example.

[0043] The base material used to produce the film-shaped processing toolis not limited to polyethylene telephthalate film, and various othermaterials may be used. Such various other materials include plasticfilms made of polyimide, polycarbonate and the like, synthetic paper,nonwoven fabric, and metal film.

[0044] The coating step which coats the mixture on the base material mayemploy a wire bar coater, a gravure coater, a reverse roller coater, aknife coater or the like.

[0045] A first embodiment of a processing method which processes awork-piece employs this embodiment of the processing tool which isproduced in the above described manner. More particularly, theprocessing tool is used to carry out a fixed-abrasive machining processwith respect to a work-piece, namely, a silicon wafer. Thefixed-abrasive machining process may be applied to a grinding processwhich grinds the surface of the wafer, a polishing film process whichpolishes the surface of the wafer, a grinding process which grinds theouter peripheral surface of the wafer, a polishing film process whichpolishes the outer peripheral surface of the wafer, and the like.

[0046] In this fixed-abrasive machining process, a grindstone made ofsilica abrasive grains or a polishing film made of silica abrasivegrains is mounted on a first embodiment of a processing apparatusaccording to the present invention, and the work-piece is ground to apredetermined dimension.

[0047] The processing apparatus used is not limited to a specific type.Any type of processing apparatus appropriate for the type of processingtool used may be employed for the fixed-abrasive machining process.

[0048] This embodiment of the processing method uses the silica abrasivegrains so that the silicon processing surface of the work-piece isprocessed with an extremely high surface quality, free of damage causedby the processing, that is, without generating residual contamination atthe processed surface. As a result, compared to the polishing processwhich is conventionally used to finish the surface of the silicon wafer,this embodiment of the processing method can obtain a comparableprocessing surface quality at a much higher efficiency. In addition,this embodiment of the processing method can realize a high shapingaccuracy (flatness). On the other hand, since this embodiment of theprocessing method does not use loose-abrasive slurry as in the case ofthe polishing process, the environment is unaffected by the process, andthe running cost of the processing apparatus can be reduced.

[0049] Next, a description will be given of a second embodiment of theprocessing tool according to the present invention and a secondembodiment of the method of producing the second embodiment of theprocessing tool.

[0050] This second embodiment of the method of producing the processingtool mixes fumed silica having an average grain diameter of 30 nm and awetting agent into a liquid acrylic resin, with the volume % of thefumed silica grains being set to 50%. A resulting mixture is stirred andmixed in a homogenizer for 5 minutes. A binder resin which is obtainedby this stirring and mixing, is subjected to a pressurized baking for 30minutes at a pressure of 50 MPa and a heating temperature of 150° C. Thebaked binder resin is further dried for 20 minutes to remove volatilecomponents, and a resin bonded grindstone made of silica abrasive grainsis obtained. In this case, the kind of binder used is not limited to aspecific resin, and it is possible to use instead any material such asresins, ceramics and metals which will not generate an endothermicreaction when the resin bonded grindstone is used to process thework-piece. In addition, the kind of method used to form the resinbonded grindstone may be appropriately selected to suit the kind ofbinder used. Furthermore, the additive (wetting agent) is also made of amaterial which will not generate an endothermic reaction when the resinbonded grindstone is used to process the work-piece.

[0051] This second embodiment of the processing tool which includes theresin bonded grindstone described above, is used in a second embodimentof the processing method which processes a work-piece. Moreparticularly, the resin bonded grindstone is mounted on a verticalinfeed grinding machine, and is used to grind the surface of thework-piece which is a 8-inch diameter silicon wafer which has alreadybeen lapped. By grinding the wafer surface for 30 seconds with amachining allowance of 30 μm, it was possible to obtain a processedsurface having a high quality such that the surface roughness is 1 nm Ryor less and the processed surface is microcrack-free when viewed on aprofile transmission electron microscope (TEM).

[0052]FIG. 1 is a diagram for explaining a second embodiment of theprocessing apparatus according to the present invention, which employsthis second embodiment of the processing method. In FIG. 1, a grindstone1 is mounted in a ring-shape on a rotary grinder 10 of a vertical infeedgrinding machine. A silicon wafer 2 which forms the work-piece is placedand held on a work-piece holder 20. The rotary grinder 10 rotates at apredetermined speed, and the work-piece holder 20 rotates in the samedirection as the rotary grinder 10 but at a speed lower than thepredetermined speed. The work-piece holder 20 rotates about a rotaryaxis different from that of the rotary grinder 10, and feeds the siliconwafer 2 to a grinding position at a constant speed, so as tocontinuously grind the surface of the silicon wafer 2 to a desireddimension.

[0053] Next, a description will be given of a third embodiment of theprocessing tool according to the present invention and a thirdembodiment of the method of producing the third embodiment of theprocessing tool.

[0054] This third embodiment of the method of producing the processingtool mixes colloidal silica having an average grain diameter of 80 nminto a liquid urethane resin, with the volume % of the colloidal silicagrains being set to 65%. A resulting mixture is stirred and mixed in ahomogenizer for 5 minutes. A binder resin which is obtained by thisstirring and mixing, is coated on a polyethylene telephthalate film to athickness of 3 μm. This film which is coated with the binder resin isheated for 10 minutes, and subjected to a drying and curing processes,so as to obtain a polishing film.

[0055] This third embodiment of the processing tool which includes thepolishing film described above, is used in a third embodiment of theprocessing method which processes a work-piece. More particularly, thepolishing film is used to polish the outer peripheral surface of the6-inch diameter silicon wafer. After 2 minutes of polishing, it waspossible to polish the outer peripheral surface of the silicon wafer toa processed surface having a high quality which is free of scratches.

[0056]FIG. 2 is a diagram for explaining a third embodiment of theprocessing apparatus according to the present invention, which employsthis third embodiment of the processing method. In FIG. 2, a polishingfilm 33 is provided between a supply spool 31 and a take-up spool 32 viarollers 21 and 22. The outer peripheral surface of the silicon wafer 2is pushed against the polishing surface of the polishing film 33,between the rollers 21 and 22. The polishing film 33 is supplied fromthe supply spool 31 and taken up on the take-up spool 32, by driving atleast the take-up spool 32 by a known driving means such as a motor, soas to polish the outer peripheral surface of the silicon wafer 2. Ofcourse, it is possible to drive both the take-up spool 32 and the supplyspool 31, so that the polishing film 33 is moved back and forth insteadof being transported in only one direction from the supply spool 31 tothe take-up spool 32.

[0057] The silicon wafer 2 may assume a fixed position relative to thepolishing film 33 during the polishing process or, may be controlled topush against the polishing film 33 with a controlled pressure.

[0058] Next, a description will be given of a fourth embodiment of theprocessing tool according to the present invention and a fourthembodiment of the method of producing the fourth embodiment of theprocessing tool.

[0059] This fourth embodiment of the method of producing the processingtool mixes colloidal silica having an average grain diameter of 30 nmand a binder into a solvent, with the volume % of the colloidal silicagrains being set to 20%. A water-soluble polymer is used as the binder,with the volume % of the water-soluble polymer being set to 30 volume %.Water is used as the solvent, with the volume % of the water being setto 50 volume %. A resulting mixture is stirred and mixed at a low speedin a state where a D.C. voltage of 10 V is applied across an anode and acathode which are inserted into the mixture, and the electrophoresis iscarried out for 60 minutes. An abrasive grain layer having a thicknesson the order of approximately 5 mm is formed around the anode, and thisabrasive grain layer is removed from the anode to form a grindstone:pellet having a thickness of 5 mm. Thereafter, this grindstone pellet isdried at a temperature of 100° C. for 1 hour, so as to finally obtain aresin bonded grindstone made of silica abrasive grains.

[0060] This fourth embodiment of the processing tool which includes theresin bonded grindstone described above, is used in a fourth embodimentof the processing method which processes a work-piece. Moreparticularly, the resin bonded grindstone is mounted on a verticalinfeed grinding machine such as that shown in FIG. 1, and is used togrind the surface of the work-piece which is a 8-inch diameter siliconwafer which has already been lapped. By grinding the wafer surface for30 seconds with a machining allowance of 30 μm, it was possible toobtain a processed surface having a high quality such that the surfaceroughness is 1 nm Ry or less and the processed surface ismicrocrack-free when viewed on the profile transmission electronmicroscope (TEM).

[0061] Next, a description will be given of further embodiments of theprocessing method according to the present invention and the processingapparatus according to the present invention, which are particularlysuited for processing a circumferential part of a thin disk-shapedwork-piece such as a semiconductor wafer. The work-piece may be made ofsemiconductor materials such as silicon, gallium arsenide and sapphire,hard and brittle materials such as quartz, glass and alumina-titaniumcarbide, and metals.

[0062] In order to facilitate the understanding of the embodimentsdescribed hereinafter, a description will first be given of thebackground technology.

[0063] A semiconductor wafer such as a silicon wafer is used as asubstrate material for a semiconductor device. Polysilicon is used asthe raw material, and a single crystal ingot is subjected to variousprocesses before the silicon wafer (bear silicon wafer) is obtained. Theactual production processes are described in a Japanese Laid-Open PatentApplication No.5-13388, for example. In the production processes, thereis a process of finishing the outer peripheral part of the wafer.

[0064] Unlike the flat top surface of the wafer, the outer peripheralsurface of the wafer does not need to have an extremely high qualitysuch that it is damage-free, since no devices are formed on the outerperipheral surface. Conventionally, the outer peripheral surface of thewafer is chamfered by a rough grinding process, and then subjected to achemical etching to remove the damage. However, extremely smallundulations and microcracks remain on the outer peripheral surface ofthe wafer which is processed in this manner. As a result, when the waferis handled during the device producing process, cracks may be formedfrom the extremely small undulations, and foreign or dust particles maybe generated from the microcracks. In addition, the strength of thewafer may deteriorate due to the existence of such cracks. Furthermore,when layers are formed on the wafer, abnormalities may be generated atlayer portions in the vicinity of the outer peripheral surface of thewafer.

[0065] Hence, according to a technique proposed in a Japanese Laid-OpenPatent Application No.5-13388, a polishing process is carried out by useof a polishing cloth after the chemical etching process, while supplyingthe slurry. The extremely small undulations and microcracks in the outerperipheral surface of the wafer can be reduced to an tolerable extent bycarrying out such a polishing process. When carrying out this polishingprocess on the outer peripheral surface of the wafer, unwoven fabric orurethane foam is mainly used for the polishing cloth, as in the case ofa polishing process carried out with respect to the flat top surface ofthe wafer. In addition, colloidal silica slurry is mainly used as theslurry, as in the case of the polishing process carried out with respectto the flat top surface of the wafer.

[0066] On the other hand, in order to prevent undulations on the outerperipheral surface of the wafer from increasing due to the chemicaletching process, a Japanese Laid-Open Patent Application No.8-236489proposes a first proposed method which omits the chemical etchingprocess. On the other hand, a mixed acid, such as a mixture ofhydrofluoric acid, nitric acid and acetic acid, when used as a chemicaletchant for the chemical etching process, causes environmental problemsunless an appropriate waste water process is carried out. Hence, thereis a second proposed method which uses an alkaline solution such as asodium hydroxide solution as the chemical etchant. But in the case ofthe second proposed method, the undulations on the outer peripheralsurface of the wafer tend to increase, and for this reason, thefinishing process which is thereafter carried out with respect to theouter peripheral surface must remove an increased amount to remove theincreased undulations. Accordingly, methods have been proposed to reducethe processing time, by carrying out a grinding process to a smallextent prior to the polishing process, when carrying out the finishingprocess with respect to the outer peripheral surface of the wafer. Suchmethods are proposed in Japanese Laid-Open Patent ApplicationsNo.9-57584 and No.9-57585, for example.

[0067] As techniques related to the finishing process with respect tothe outer peripheral surface of the wafer, various proposals have beenmade on the processing method and the processing apparatus which carryout a process on a work-piece, and the processing tool and the method ofproducing the processing tool which is used for such a process.

[0068] For example, processing methods and processing apparatuses whichuse a polishing cloth as the processing tool and carry out the finishing(polishing) process while supplying the slurry, are proposed in JapaneseLaid-Open Patent Applications No.5-6881, No.5-23959, No.5-123952,No.5-243196, No.7-50279, No.9-94746, No.10-29142, No.10-71549,No.10-328989 and No.11-70450. In addition, the polishing cloth isproposed in a Japanese Laid-Open Patent Application No.5-152260, forexample. A processing tool which is made of a material with a hardnessgreater than unwoven fabric or the like, such as cast iron and stainlesssteel, has also been proposed. But as noted in a Japanese Laid-OpenPatent Application No.10-71549, for example, a mirror finishing isdifficult by use of a processing tool which has a high hardness, andsuch a processing tool is suited for use in a rough grinding processrather than the finishing (polishing) process.

[0069] On the other hand, a linear cutout called an orientation flat isprovided on the outer peripheral surface of the wafer. This orientationflat is used as a reference for the purpose of positioning the wafer oraligning the crystal orientation of the wafer when carrying out a deviceproducing process. Recently, the cutout forming the orientation flat hasbecome smaller, so as to enable a larger number of chips to beaccommodated on one wafer. Moreover, an arcuate or V-shaped cutoutcalled a notch is popularly used as the orientation flat. The cutoutpart can be made small by using the notch. Hence, there is a furtheradvantage in that the balance of motion is improved when the wafer isrotated during various processes including a drying process.

[0070] The orientation flat part or the notch part has a shape quitedifferent from the continuous outer peripheral surface of the wafer. Forthis reason, various processing methods and processing tools have beendeveloped for the orientation flat part or the notch part, which arequite different from the processing methods and processing toolsdeveloped for the continuous outer peripheral surface of the wafer. Forexample, a Japanese Laid-Open Patent Application No.7-50279 proposes atechnique which can improve the processing speed by using differentpolishing cloths for the outer peripheral surface and the orientationflat part of the wafer. In addition, methods and apparatuses forfinishing the notch part are proposed in Japanese Laid-Open PatentApplications No.7-1322, No.8-168947 and No.8-236490. All of thesemethods and apparatuses basically use a polishing cloth as theprocessing tool, and carry out the finishing (polishing) process whilesupplying slurry. The Japanese Laid-Open Patent Application No.8-168947also takes into consideration the use of a polishing belt or a polishingfilm as the processing tool.

[0071] The proposed methods and apparatuses described above carry outthe loose-abrasive polishing process to finish the surface of the waferusing the polishing cloth while supplying the slurry. However, theloose-abrasive polishing process have problems in that the processingenvironment is harsh, the waste water must be processed, the runningcost of the processing system is high, and the processing efficiency islow. For this reason, there are proposals to carry out the finishing(polishing) process on the wafer by a fixed-abrasive machiningapparatus, that is, by use of a fixed-abrasive grinding tool.

[0072] Various processing methods and processing apparatuses which use apolishing film as the fixed-abrasive grinding tool, and techniquesrelated thereto are proposed for example in Japanese Laid-Open PatentApplications No.7-100748, No.7-171749, No.7-237100 and No.8-168946.

[0073] For example, Japanese Laid-Open Patent Applications No.7-100748,No.7-124853, No.8-118226 and No.9-76148 propose processing methods andprocessing apparatus which use a polishing film as the processing toolfor processing the orientation flat part or the notch part of the wafer.

[0074] Other processing methods use a grindstone as the fixed-abrasivegrinding tool. Such processing methods are proposed in JapaneseLaid-Open Patent Applications No.6-210520, No.7-58065, No.8-90401,No.8-197400 and No.10-189508, for example.

[0075] Therefore, the loose-abrasive polishing process which uses thepolishing cloth and the slurry to finish the outer peripheral surface ofthe wafer have problems from the point of view of the waste waterprocess which is required and the high running cost of the processingapparatus. In addition, the processing efficiency of the loose-abrasivepolishing process is low in general, and it takes approximately 7minutes to finish the outer peripheral surface of one wafer. Compared toother processes such as a lapping process carried out with respect tothe top and bottom surfaces of one wafer which only requiresapproximately 1 to 2 minutes, it may be seen that the processingefficiency of the loose-abrasive polishing process is low. Accordingly,there are demands to improve the processing efficiency, by the use of afixed-abrasive grinding tool such as the polishing film and thegrindstone.

[0076] However, the conventional processing methods used to finish theouter peripheral surface of the wafer do not take into consideration theoptimization of the processing tool used for each part of the wafer. Inother words, the conventional processing methods change the conditionsunder which the processing tool is used with respect to specific partsof the wafer, but do not optimize the processing tool for each part ofthe wafer by changing the processing tool for each part of the wafer,for example. Because the processing tool is not optimized for each partof the wafer to be processed, the following problems occur.

[0077] In the case where the grindstone is used as the fixed-abrasivegrinding tool, the grindstone must normally be moved at a tool speed onthe order of several hundred m/min or greater in order to carry out asatisfactory grinding process. Accordingly, a high tool speed can berealized with respect to the outer peripheral surface of the wafer sinceit is possible to use a grindstone having a large diameter, but asufficiently high tool speed cannot be realized with respect to thenotch part of the wafer since it is only possible to use a grindstonehaving a small diameter. As a result, there are problems in that thewear of the grindstone is large, the tool life is short, the loading ofthe grindstone easily occurs, the shaping accuracy of the notch parteasily deteriorates, and the quality of the processed surface isextremely poor at the notch part of the wafer as compared to that at theouter peripheral part of the wafer. It is conceivable to use agrindstone having a large diameter to process the notch part of thewafer, but in this conceivable case, it becomes necessary to control thegrindstone so that a rotary axis of the grindstone becomes parallel tothe wafer surface. But the outer peripheral surface of the wafer,including the notch part, is chamfered. For this reason, in order toprocess the wafer by controlling the rotary shaft of the grindstone tobecome parallel to the wafer surface, it would be necessary to carry outthe grinding process separately at three locations, namely, the upperportion of the chamfered part, a central portion of the chambered part,and a lower portion of the chambered part of the wafer. As a result, itwould be impossible to reduce the processing time.

[0078] On the other hand, compared to the grindstone, the capability ofholding the abrasive grains and the strength or rigidity of thepolishing film are low. In addition, the tool speed is relatively low inthe case of the polishing film, and the removing efficiency realized bythe polishing film is low as compared to that of the grindstone. As aresult, when the polishing film is used to finish the entire outerperipheral surface of the wafer, it is impossible to reduce theprocessing time.

[0079] Problems similar to the problems described above with respect tothe semiconductor wafer also occur when processing the outer peripheralsurface of a disk or wafer made of materials such as metals and hard andbrittle materials such as quartz, glass and alumina-titanium carbide. Inthe case of a donut-shaped glass disk, problems similar to thosedescribed above which are encountered when processing the outerperipheral surface and the cutout part of the wafer, also occur whenprocessing an inner peripheral surface defining a center hole of thedonut-shaped glass disk. Recently, the loose-abrasive polishing processis carried out with respect to the center hole of the glass disk inorder to prevent generation of foreign or dust particles and to improvethe mounting accuracy of the glass disk with respect to a disk unit.Consequently, the loose-abrasive polishing process carried out withrespect to the center hole of the glass disk also results in problems inthat the processing environment is harsh, the waste water must beprocessed, the running cost of the processing system is high, and theprocessing efficiency is low. Hence, it is conceivable to process thecenter hole of the glass disk by use of a grindstone, but in this case,it would only be possible to use a grindstone having a small diameter,similarly as when processing the cutout part at the outer peripheralsurface of the wafer. Therefore, the use of the grindstone to processthe center hole of the glass disk would result in problems in that asufficiently high tool speed cannot be obtained and the wear of thegrindstone is large.

[0080] On the other hand, Japanese Laid-Open Patent ApplicationsNo.9-123050, No.10-44007 and No.11-70450 point out a problem caused bythe use of the polishing film or the polishing cloth. In other words,marks, scratches or the like matching a transport direction of thepolishing film or the polishing cloth is inevitably formed on theprocessed surface.

[0081] According to the technique proposed in the Japanese Laid-OpenPatent Application No.8-90401, a grindstone including silica abrasivegrains is used to process the outer peripheral part of the wafer to amirror finish, while supplying a water-soluble processing fluid. Butaccording to the experiments conducted by the present inventors, it wasconfirmed that the use of the water-soluble processing fluid suppressesthe mechano-chemical reaction of silica with respect to silicon, and theremoving effect caused thereby is virtually lost, thereby making itextremely difficult to realize the desired polishing process. On theother hand, the Japanese Laid-Open Patent Application No.8-197400proposes a technique which uses a grindstone made of fine abrasivegrains and a elastic binder for the purposes of polishing the outerperipheral part of the wafer. However, in order to process the outerperipheral part of the wafer to a processed surface with a qualitycomparable to a mirror finish, the mechano-chemical processing isessential. Hence, it is extremely difficult to obtain a processedsurface having a high quality solely by the mechanical removal asproposed in the Japanese Laid-Open Patent Application No.8-197400.

[0082] Accordingly, the further embodiments of the processing methodaccording to the present invention and the processing apparatusaccording to the present invention are designed to eliminate the abovedescribed problems, and are particularly suited for processing acircumferential part of a thin disk-shaped work-piece such as asemiconductor wafer.

[0083]FIG. 3 is a diagram showing the general construction of a fifthembodiment of the processing apparatus according to the presentinvention. This fifth embodiment of the processing apparatus employs afifth embodiment of the processing method according to the presentinvention.

[0084] A processing apparatus 100 shown in FIG. 3 includes a grindingunit 110, a transport unit 120, and a film polishing unit 130 which arearranged on mutually independent blocks and are independentlycontrollable by a controller (not shown).

[0085] The grinding unit 110 includes a work moving section 111 and agrinding section 112 which are both mounted on a base of thecorresponding block.

[0086] In the work moving section 111, a slide table 114 is slidablyprovided on a pair of guide rails 113 which are provided on the base ofthe corresponding block. The slide table 113 is slidable in horizontaldirections indicated by arrows in FIG. 3. A mechanism (not shown) formoving the slide table 114 may be realized by a known means such as astructure which rotates an integrated guide-and-ball-screw by a motor,or a rack and pinion structure.

[0087] A work rotating motor 115 which is linked to a work table 116 isfixed on the slide table 114. A plurality of vacuum suction pads (notshown) are provided in the work table 116. A disk-shaped work-piece 102,such as a disk and a wafer, is placed and positioned on the work table116 by the transport unit 120, and is held in position on the work table116 under suction from under the work table 116 via the vacuum suctionpads.

[0088] In the grinding section 112, a frame 117 is provided on one sideof the guide rails 113, opposite to the transport unit 120. A pair ofguide rails (not shown) extend vertically on the frame 117, and a slider150 is slidably supported on these vertical guide rails. An elevatormechanism (not shown) which moves the slider 150 up and down, may berealized by a known means such as a structure which rotates anintegrated guide-and-ball-screw by a motor, or a rack and pinionstructure.

[0089] A grinding motor 119 is fixed on the slider 150. A grindstone 103is linked to a rotary shaft of the grinding motor 119.

[0090] The grindstone 103 is made of abrasive grains which generate amechano-chemical reaction when used to polish a surface of thework-piece 102 or, made of a binder mixture such as resins, ceramics andmetals which include such abrasive grains. An average grain diameter ofthe abrasive grains is set in a range of 0.8 nm to 10 μm. If the averagegrain diameter used for the grindstone 103 is less than 0.8 nm, themechanical action on the work-piece 102 becomes too small, and a desiredmechano-chemical reaction cannot be generated. On the other hand, if theaverage grain diameter used for the grindstone 103 exceeds 10 μm, themechanical action becomes too large, and there is a possibility ofgenerating damage to the outer peripheral surface of the work-piece 102which is processed.

[0091] For example, the method described above may be employed toproduce the grindstone 103 which includes silica abrasive grains. Inthis embodiment, the grindstone 103 has a multi-level structure as shownin FIG. 4. A plurality of tapered grooves 103 a through 103 c are formedon the outer peripheral surface of the cylindrical grindstone 103. Whenpolishing the outer peripheral surface of the work-piece 102, the outerperipheral surface of the work-piece 102 is pushed against one of thetapered grooves 103 a through 103 c of the grindstone 103. As thegrindstone 103 wears out due to friction, the tapered groove which isused for the polishing process may be appropriately changed among thetapered grooves 103 a through 103 c.

[0092] As described above and in Japanese Laid-Open Patent ApplicationNo.2000-190228 and Japanese Patent Application No.11-82171, for example,silica abrasive grains are used as the abrasive grains which generatethe mechano-chemical reaction when used to polish the surface of thework-piece 102 which is made of silicon. However, it is also possible touse grains made of other materials, such as barium carbonate grains, asthe abrasive grains which generate the mechano-chemical reaction.Furthermore, when the work-piece 102 is made of glass, for example, itis possible to use cerium oxide grains as the abrasive grains whichgenerate the mechano-chemical reaction.

[0093] The transport unit 120 has a swivel shaft mounted on thecorresponding block or the floor. The transport unit 120 includes arobot hand (or a link section) 123, a pivot section 121 which turns thelink section 123 in a horizontal direction, and a slider section 122which is arranged on the pivot section 121 and moves the link section123 up and down. One end of the link section 123 is linked to the pivotsection 121 and the slider section 122, and the other end of the linksection 123 is provided with vacuum suction pads.

[0094] For example, the pivot section 121 transmits a torque generatedfrom a D.C. servo motor to the link section 123 via a gear mechanism(not shown). A rotary angle of the link section 123 is obtained in theform of an electrical signal which is fed back to the controllerdescribed above.

[0095] For example, the slider section 122 rotates a ball screw, acontinuous-thread screw or the like by a D.C. servo motor, andtransforms this rotary motion into a linear motion via a slide bearing,a rod and the like. A moving distance of the link section 123 whichmoves up and down, is obtained in the form of an electrical signal whichis fed back to the controller described above.

[0096] Manipulation functions such as moving, positioning and fixing thework-piece 102 are realized by the feedback control based on the drivenamounts of the link section 123, the pivot section 121 and the slidersection 122. In other words, the work-piece 102 is transported by a beltconveyor or the like from a previous processing stage (not shown), andis moved and placed one by one on the work table 116 of the grindingunit 110. On the other hand, the work-piece 102 after being ground ofthe outer peripheral surface by the grinding unit 110 is moved andplaced on a work table 137 of the polishing unit 130.

[0097] The polishing unit 130 includes a work moving section 133 and apolishing section 132 which are both mounted on a based on thecorresponding block.

[0098] In the work moving section 133, a slide table 135 is slidablyprovided on a pair of guide rails 134 which are provided on the base ofthe corresponding block. The slide table 135 is slidable in horizontaldirections indicated by arrows in FIG. 3. A mechanism (not shown) formoving the slide table 135 may be realized by a known means such as astructure which rotates an integrated guide-and-ball-screw by a motor,or a rack and pinion structure.

[0099] A work rotating motor 136 which is linked to the work table 137is fixed on the slide table 135. For example, a stepping motor may beused for the work rotating motor 136. A plurality of vacuum suction pads(not shown) are provided in the work table 137. The work-piece 102 isplaced and positioned on the work table 137 by the transport unit 120,and is held in position on the work table 137 under suction from underthe work table 137 via the vacuum suction pads.

[0100] In the polishing section 132, a tape-shaped polishing film 101 iswound on a supply reel 140 in a state free to be supplied therefrom, andthe supplied polishing film 101 is taken up on a take-up reel 139 via apressing roller 141. Motors (not shown) which drive the supply reel 140and the take-up reel 139 are both rotatable in forward and reversedirections. By controlling the two motor in synchronism, the polishingfilm 101 is transported upwards and downwards in FIG. 3 to polish thework-piece 102 which is positioned and held on the work table 137. Moreparticularly, the polishing film 101 presses against a cutout part 102 aof the work-piece 102 shown in FIG. 5 on the work table 137 while beingtransported upwards and downwards, to polish the cutout part 102 a.

[0101] As shown in FIG. 6, the polishing film 101 includes a resin film110 a which forms the base material, and a binder resin 101 b whichincludes abrasive grains 101 c which generate the mechano-chemicalreaction when processing the surface of the work-piece 102. The binderresin 101 b is coated on the resin film 101 a, and then dried and cured.For the reasons described above, the average grain diameter of theabrasive grains 101 c is set in a range of 0.8 nm to 10 μm. For example,the method described above may be employed to produce the polishing film101 which includes silica abrasive grains as the abrasive grains 101 c.Silica abrasive grains are used as the abrasive grains 101 c whichgenerate the mechano-chemical reaction when used to polish the surfaceof the work-piece 102 which is made of silicon. However, it is alsopossible to use grains made of other materials, such as barium carbonategrains, as the abrasive grains 101 c which generate the mechano-chemicalreaction. Furthermore, when the work-piece 102 is made of glass, forexample, it is possible to use cerium oxide grains as the abrasivegrains 101 c which generate the mechano-chemical reaction.

[0102] When carrying out the polishing process, the side of thepolishing film 101 having the abrasive grains 101 c is pressed againstthe cutout part 102 a of the work-piece 102 by the pressing roller 141.The cutout part 102 a is polished by transporting the polishing film 102upwards and/or downwards in FIG. 3. A width (tape width) of thepolishing film 101 is set slightly larger than a width of the cutoutpart 102 a.

[0103] A pressing unit 131 includes a frame 141-1 which is provided onthe side of the polishing film 101 having the resin film 101 a androtatably supports the pressing roller 141, an air cylinder 138 whichcan move the frame 141-1 in the right and left directions, and aswinging mechanism which uses a driving motor (not shown) to swing orrotate the frame 141-1 in a back and forth direction which isperpendicular to the transport direction of the polishing film 101. Thepressing roller 141 is made of a resilient material or at least theouter periphery of the pressing roller 141 is sufficiently compliant.The outer peripheral shape, thickness and the like of the pressingroller 141 correspond to those of the cutout part 102 a. The aircylinder 138 is controlled by the controller, described above, so that apolishing pressure of the polishing film 101 becomes a predeterminedvalue. When carrying out the polishing process, the frame 141-1 ispushed so as to press the polishing film 101 against the work-piece 102.

[0104] Details of the grinding unit 110 and the polishing unit 130 maybe found in Japanese Laid-Open Patent Applications No.8-90401 andNo.9-76148, for example.

[0105] The work-piece 102 may be positioned based on an imagerecognition made with respect to the top surfaces of the work tables 116and 137 using a sensor, such as a television camera, a CCD image sensorand a vidicon. In this case, an image recognition result is processed ona personal computer or the like, and a center coordinate of thework-piece 102 is obtained with reference to marks which are providedbeforehand on the work tables 116 and 137. The movement of the linksection 123 is controlled based on the obtained center coordinate. Onthe other hand, a sensor (not shown) is mounted on a tip end of the linksection 123, so that by recognizing the image of the work-piece 102which is held, a positioning mechanism can finely adjust the relativepositions of the work-piece 102 relative to the work tables 116 and 137.This type of a positioning mechanism is described in a JapaneseLaid-Open Patent Application No.11-207611, for example.

[0106] Next, a description will be given of this fifth embodiment of theprocessing method which finishes the outer peripheral surface of thework-piece 102. It is assumed for the sake of convenience that thework-piece 102 is a disk which includes the cutout part (notch part) 102a and has already been subjected to a pre-processing at a previousprocessing stage including at least a chamfering process, a lappingprocess and an etching process such as a chemical etching process.

[0107] This fifth embodiment of the processing method includes agrinding step which grinds the outer peripheral surface of thework-piece 102, that is, the circumferential surface of the disk, and apolishing step which polishes the cutout part 102 a on the outercircumferential surface of the work-piece 102.

[0108] First, a description will be given of the grinding step.

[0109] In the transport unit 120, the work-piece 102 which istransported from the previous processing stage by the conveyor belt orthe like is held by the link section 123 under suction via the vacuumsuction pads, and is moved and placed one by one on the work table 116of the grinding unit 110. In this state, the slide table 114 is lockedby a locking mechanism (not shown) so as to stop at a predeterminedposition. A position alignment is made so that in the state where thework table 116 is stationary, the center of rotation of the work table116 and the center of the work-piece 102 match.

[0110] Next, in the grinding unit 110, the work-piece 102 which isaligned of its position is held on the work table 116 by the vacuumsuction pads of the work table 116. The slide table 114 and the slider150 are moved, so as to position the grindstone 103 and the work-piece102 to predetermined positions.

[0111] Then, the work table 116 and the grindstone 103 are rotated, andthe slide table 114 is moved in a horizontal direction towards thegrindstone 103, so that the outer circumferential surface of thework-piece 102 contacts one of the tapered grooves 103 a through 103 cof the grindstone 103. Furthermore, the slide table 114 is moved by apredetermined quantity, so as to form a chamfered part of the work-piece102 into a mirror finish.

[0112] After the mirror finishing process ends, the rotations of thework table 116 and the grindstone 103 are stopped. In addition, theslide table 114 is moved in a horizontal direction towards the transportunit 120 and stopped at a predetermined waiting position.

[0113] Next, a description will be given of the polishing step.

[0114] After the grinding process, the pivot section 121 of thetransport unit 120 turns the link section 123 by a predetermined amounttowards the grinding unit 110, and further, the slider section 122lowers the link section 123 by a predetermined amount. By this operationto turn and lower the link section 123, the vacuum suction pads of thelink section 123 make contact with the work-piece 102 on the work table116. The work-piece 102 is thus held under suction from above by thevacuum suction pads of the link section 123, and the suction from underthe work table 116 is released. Next, after the slider section 122raises the link section 123 by a predetermined amount, the pivot section121 turns the link section 122 by a predetermined amount towards thefilm polishing unit 130. Moreover, the slider section 122 lowers thelink section 123 by a predetermined amount, and moves and places thework-piece 102 which is held under suction by the link section 123 ontothe work table 137. In this state, a position alignment is made so thatthe center of rotation of the work table 137 and the center of thework-piece 102 match, and the outer periphery of the pressing roller 141and the cutout part 102 a of the work-piece 102 confront each other.When making this position alignment, the work table 137 is turned ifnecessary.

[0115] Then, in the film polishing unit 130, the work-piece 102 which isaligned of its position is held by the vacuum suction pads of the worktable 137 from under the work-piece 102, and the suction of the linksection 123 is released. Thereafter, the slider section 122 raises thelink section 123 by a predetermined amount, and the pivot section 121turns the link section 123 by a predetermined amount towards thegrinding unit 110.

[0116] Next, the slide table 135 is moved by a predetermined amounttowards the polishing section 132, so as to move the work-piece 102close to the pressing roller 141. Thereafter, the air cylinder 138 isdriven, so that the polishing film 101 which is pushed by the pressingroller 141 presses against the cutout part 102 a of the work-piece 102at a predetermined polishing pressure.

[0117] Then, the take-up reel 139 and the supply reel 140 are driven totransport the polishing film 101 vertically, back and forth, so as topolish the cutout part 102 a by the polishing film 101 which is pushedby the pressing roller 141. In this state, a boundary between the cutoutpart 102 a and the outer circumferential part of the work-piece 102 ispolished by rotating the work table 137 in the forward and reversedirections by a necessary amount. In addition, the frame 141-1 is madeto swing up and down if necessary, by the driving motor and the swingingmechanism described above.

[0118] After polishing the cutout part 102 a of the work-piece 102, thedriving of the take-up reel 139, the supply reel 140 and the aircylinder 138 are stopped, so that the pressing roller 141 recedes fromthe polishing position.

[0119] The pivot section 121 of the transport unit 120 then turns thelink section 123 by a predetermined amount towards the film polishingunit 130, and the slider section 122 lowers the link section 123 by apredetermined amount. By this turning and lower operation, the vacuumsuction pads of the link section 123 makes contact with the work-piece102 on the work table 137 and holds the work-piece 102 from above bysuction. Further, the suction from under the work table 137 is released.

[0120] Next, after the slider section 122 raises the link section 123 bya predetermined amount, the pivot section 121 turns the link section 123towards the next processing stage (not shown). For example, the nextprocessing stage carries out an air cleaning process with respect to thework-piece 102 which is transported thereto.

[0121] According to this embodiment, the polishing film 101 istransported in directions perpendicular to the top or bottom surface ofthe work-piece 102. However, it is of course possible to transport thepolishing film 101 in a direction parallel to the top or bottom surfaceof the work-piece 102. Such a parallel transport of the polishing filmis proposed in a Japanese Laid-Open Patent Application No.7-124853, forexample.

[0122] Moreover, this embodiment was described above along the transportpath through which the work-piece 102 is transported. However, since theblock of the grinding unit and the block of the film polishing unit areindependent of each other, it is of course possible to carry out thecontrol so that the grinding unit and the film polishing unit carry outthe processes simultaneously with respect to two different work-pieces.

[0123] Next, a description will be given of a sixth embodiment of theprocessing apparatus according to the present invention, by referring toFIG. 7. FIG. 7 is a diagram showing the general construction of thesixth embodiment of the processing apparatus according to the presentinvention. This sixth embodiment of the processing apparatus employs asixth embodiment of the processing method according to the presentinvention. In FIG. 7, those parts which are the same as thosecorresponding parts in FIG. 3 are designated by the same referencenumerals, and a description thereof will be omitted.

[0124] In this sixth embodiment, the present invention is applied to theprocessing of a peripheral surfaces of a donut-shaped work-piece such asa glass disk. More particularly, the film polishing unit 130 shown inFIG. 3 is replaced by a film polishing unit 130A shown in FIG. 7. Afterthe outer circumferential surface of a donut-shaped work-piece 102A isprocessed by the grinding unit 110 shown in FIG. 3, the film polishingunit 130A processes the inner peripheral surface defining the centerhole in the donut-shaped work-piece 102A.

[0125] In a work moving section 133A of the film polishing unit 130A, aslide table 135 is slidably provided on a pair of guide rails 134 whichare provided on the base of the corresponding block. The slide table 135is slidable in horizontal directions indicated by arrows in FIG. 7. Amechanism (not shown) for moving the slide table 135 may be realized bya known means such as a structure which rotates an integratedguide-and-ball-screw by a motor, or a rack and pinion structure.

[0126] A work rotating motor 136 which is linked to a work table 137A isfixed on the slide table 135. For example, a stepping motor may be usedfor the work rotating motor 136. The work table 137A has a centeropening which is larger than the center hole of the work-piece 102A, anda plurality of vacuum suction pads (not shown) on the outer periphery ofthe center opening. In a plan view, an inner peripheral surface definingthe center opening of the work table 137A surrounds the inner peripheralsurface defining the center hole in the work-piece 102A. The work-piece102A is held in position on the work table 137A under suction from underthe work table 137A via the vacuum suction pads.

[0127] In a polishing section 132A, a tape-shaped polishing film 101A iswound on a supply reel 140A in a state free to be supplied therefrom,and the supplied polishing film 101A is taken up on a take-up reel 139Avia a pressing roller 141A. Motors (not shown) which drive the supplyreel 140A and the take-up reel 139A are both rotatable in forward andreverse directions. By controlling the two motor in synchronism, thepolishing film 101A is transported to the left and right between thesupply and take-up reels 140A and 139A in FIG. 7 to polish the innerperipheral surface defining the center hole of the work-piece 102A whichis positioned and held on the work table 137A. More particularly, thework-piece 102A on the work table 137A is rotated at a predeterminedspeed by the work rotating motor 136, while the pressing roller 141Apushes the polishing film 101A against the inner peripheral surfacedefining the center hole of the work-piece 102A, so that the innerperipheral surface of the work-piece 102A is polished by the polishingfilm 101A. A tape width of the polishing film 101A is smaller than adiameter of the center hole of the work-piece 102A but larger than awidth of the pressing roller 141A. The polishing film 101A can beproduced in the same manner as the polishing film 101 of the fifthembodiment described above. In this sixth embodiment, cerium oxidegrains are used as the abrasive grains 101 c which generate themechano-chemical reaction when processing the work-piece 102A.

[0128] A pressing unit 131A includes a frame 141A-1 which is provided onthe base material side of the polishing film 101A and rotatably supportsthe pressing roller 141A, an air cylinder 138A which moves the frame141A-1 back and forth in perpendicular directions towards the paper andfrom the paper in FIG. 7 and up and down in vertical directions in FIG.7, and a swinging mechanism (not shown). The switching mechanism uses adriving motor (not shown) to swing the frame 141A-1 in directions to theleft and right in FIG. 7. The pressing roller 141A is made of aresilient or sufficiently compliant material. The outer peripheralshape, thickness and the like of the pressing roller 141A are setcorrespondingly to the shape of the inner peripheral surface of thework-piece 102A. The air cylinder 138A moves the frame 141A-1 in amanner described above, so as to push the abrasive grain side of thepolishing film 101A by the pressing roller 141A against the innerperipheral surface of the work-piece 102A.

[0129] When carrying out the polishing process with respect to the innerperipheral surface of the work-piece 102A, the work-piece 102A havingthe outer peripheral surface thereof already subjected to the grindingprocess by the grinding unit 110 is transported by the transport unit120 to the film polishing unit 130A, similarly as in the case of thefifth embodiment described above. The position of the transportedwork-piece 102A is aligned so that the center of rotation of the worktable 137A matches the center of the work-piece 102A, and the outerperiphery of the pressing roller 141A confronts the inner peripheralsurface of the work-piece 102A.

[0130] Next, in the film polishing unit 130A, the work-piece 102A whichis aligned of its position is held on the work table 137A by suction viathe vacuum suction pads. Thereafter, the air cylinder 138A is driven toappropriately move the frame 141A-1 up, down, right and/or left bypredetermined amounts, so as to make the pressing roller 141A approachthe inner peripheral surface of the work-piece 102A. As a result, thepressing roller 141A makes the polishing film 101A contact the innerperipheral surface of the work-piece 102A with a predetermined polishingpressure.

[0131] Then, the take-up reel 139A and the supply reel 140A are drivento transport the polishing film 101A left and right, while rotating thework table 137A at a predetermined speed, so as to polish the innerperipheral surface of the work-piece 102A. In addition, the swingingmechanism and the driving motor swing the frame 141A-1 back and forthtowards the paper and away from the paper in FIG. 7, if necessary.

[0132] After polishing the inner peripheral surface of the work-piece102A, the driving of the take-up and supply reels 139A and 140A, therotating of the work table 137A, and the driving of the air cylinder138A are stopped, so as to make the pressing roller 141A recede from thepolishing position.

[0133] Next, the transport unit 120 shown in FIG. 3 transports thework-piece 102A which has been subjected to the processes in thegrinding unit 110 and the film polishing unit 130A to the an aircleaning unit (not shown) which carries out the next air cleaningprocess with respect to the work-piece 102A.

[0134] According to the fifth and sixth embodiments, the grindstone 103is used to process the outer peripheral part of the work-pieces 102 and102A having the relatively large processing surface. Since thegrindstone 103 may have a large diameter, it is possible to obtain asufficiently high tool speed when processing the outer peripheral partof the work-pieces 102 and 102A. In addition, the flexible polishingfilm 101 is used to process the cutout part (notch part) 102 a of thework-piece 102 having the relatively small processing surface and a morecomplicated shape. The flexible polishing film 101A is used to processthe inner peripheral part of the work-piece 102A having a relativelysmall processing surface, such that the diameter of the tool usable forthe inner peripheral part is small compared to that usable for the outerperipheral part. Therefore, it is possible to stably process thesurfaces of the work-pieces 102 and 102A with a high efficiency. Freshunworn parts of the polishing films 101 and 101A can always be used bymerely controlling the supply reel 140 or 140A and the take-up reel 139or 139A, thereby preventing the loading.

[0135] Moreover, the grindstone 103 and the polishing films 101 and 101Aused in the fifth and sixth embodiments may be made of abrasive grainswhich generate the mechano-chemical reaction when processing the surfaceof the work-piece 102 or 102A, such as silica abrasive grains, bariumcarbonate abrasive grains and cerium oxide abrasive grains. By usingsuch abrasive grains, it is possible to obtain a high-quality processedsurface comparable to that obtained by the conventional loose-abrasivepolishing process, even when applied to the fixed-abrasive grindingtool.

[0136] In addition, the fifth and sixth embodiments carry out a drygrinding process and a dry polishing process. A mechano-chemical processcan be carried out by use of the abrasive particles which generate themechano-chemical reaction when processing the work-piece. At the sametime, it is possible to suppress the deterioration of the workingenvironment and the increase of the running cost which would otherwiseoccur due to the need to supply processing fluids such as the slurry andcarry out the waste water process.

[0137] Further, the fifth and sixth embodiments can not only carry outthe mechano-chemical process, but also prevent marks, scratches and thelike from being formed on the processed surface of the work-piece in thetransport direction of the polishing film or the like.

[0138] It was confirmed through experiments conducted by the presentinventors that the outer peripheral part, the cutout part of the outerperipheral part and the inner peripheral part of a 8-inch diametersilicon wafer can be processed to a mirror finish comparable to thatobtained by use of the conventional loose-abrasive polishing processwhen the grindstone 103 and the polishing film 101 or 101A having thefollowing characteristics. That is, silica abrasive grains having aprimary average grain diameter of 20 nm was used as the abrasive grains.In addition, a resin bonded grindstone using a phenol resin as thebinder was used for the grindstone 103. Moreover, a film which uses apolyethylene telephthalate as the base material and an urethane resin asthe binder was used as the polishing film 101 or 101A. It was possibleto complete the processing on the outer peripheral part of the siliconwafer in 1 minute, starting from the transport of the silicon wafer intothe processing apparatus 100 to the transport of the processed wafer outfrom the processing apparatus 100. This processing time of 1 minute isextremely short when compared to 7 minutes which would be required tocarry out a similar process on the outer peripheral part of the siliconwafer by the conventional loose-abrasive polishing process. Furthermore,no marks, scratches and the like were formed on the processed surface ofthe silicon wafer in the transport direction of the polishing film 101or 101A.

[0139] Further, the present invention is not limited to theseembodiments, but various variations and modifications may be madewithout departing from the scope of the present invention.

What is claimed is:
 1. A processing tool for carrying out afixed-abrasive grinding process on a surface of a silicon work-piece,comprising: abrasive grains made up silica grains.
 2. The siliconprocessing tool as claimed in claim 1, wherein a primary average grainsize of the silica grains is 0.8 nm to 10 μm.
 3. The processing tool asclaimed in claim 1, wherein a content of the silica grains in theabrasive grains is 10 to 70 volume percent.
 4. The processing tool asclaimed in claim 1, further comprising: a binder bonding the abrasivegrains, said binder being made of a material which generates noendothermic reaction during the process carried out on the siliconwork-piece.
 5. The processing tool as claimed in claim 1, furthercomprising: an additive mixed to the abrasive grains, said additivebeing made of a material which generates no endothermic reaction duringthe process carried out on the silicon work-piece.
 6. The processingtool as claimed in claim 1, wherein the abrasive grains form agrindstone.
 7. The processing tool as claimed in claim 1, wherein theabrasive grains form a film.
 8. The processing tool as claimed in claim7, wherein the film is flexible.
 9. A method of producing a processingtool having abrasive grains for carrying out a fixed-abrasive grindingprocess on a surface of a silicon work-piece, said method comprising thestep of: (a) mixing a binder and silica grains to form a mixture; and(b) forming the mixture into the abrasive grains of the processing tool.10. The method of producing the processing tool as claimed in claim 9,wherein said step (a) uses silica grains having a primary average grainsize of 0.8 nm to 10 μm.
 11. The method of producing the processing toolas claimed in claim 9, wherein said step (a) uses a content of thesilica grains in the abrasive grains in a range of 10 to 70 volumepercent.
 12. The method of producing the processing tool as claimed inclaim 9, wherein said step (a) uses a binder made of a material whichgenerates no endothermic reaction during the process carried out on thesilicon work-piece by the processing tool.
 13. A processing method forcarrying out a fixed-abrasive grinding process on a surface of a siliconwork-piece, comprising the steps of: (a) positioning the siliconwork-piece relative to a processing tool having abrasive grains made upsilica grains; and (b) processing the surface of the silicon work-pieceby the abrasive grains of the processing tool.
 14. The processing methodas claimed in claim 13, wherein the silica grains have a primary averagegrain size of 0.8 nm to 10 μm.
 15. The processing method as claimed inclaim 13, wherein a content of the silica grains in the abrasive grainsin a range of 10 to 70 volume percent.
 16. The processing method asclaimed in claim 13, wherein the tool includes a binder which bonds theabrasive grains and is made of a material which generates no endothermicreaction during the process carried out on the silicon work-piece.
 17. Aprocessing method for carrying out a process on a disk-shaped ordonut-shaped work-piece, comprising the steps of: (a) grinding an outerperipheral surface of the work-piece by a grindstone; and (b) polishingcutout part on the outer peripheral surface of the work-piece and/or aninner peripheral surface of the work-piece by a polishing film.
 18. Theprocessing method as claimed in claim 17, wherein said step (a) uses agrindstone including abrasive grains which generate mechano-chemicalreaction with respect to a processing surface of the work-piece.
 19. Theprocessing method as claimed in claim 18, wherein the abrasive grainshave a primary average grain size of 0.8 nm to 10 μm.
 20. The processingmethod as claimed in claim 17, wherein said step (b) uses a polishingfilm including abrasive grains which generate mechano-chemical reactionwith respect to a processing surface of the work-piece.
 21. Theprocessing method as claimed in claim 20, wherein said step (b) uses aflexible polishing film.
 22. The processing method as claimed in claim20, wherein the abrasive grains have a primary average grain size of 0.8nm to 10 μm.
 23. The processing method as claimed in claim 17, whereinsaid steps (a) and (b) respectively carry out a dry grinding process anda dry polishing process.
 24. A processing apparatus for carrying out aprocess on a disk-shaped or donut-shaped work-piece, comprising: agrinding unit grinding an outer peripheral surface of the work-piece bya grindstone; a polishing unit polishing cutout part on the outerperipheral surface of the work-piece and/or an inner peripheral surfaceof the work-piece by a polishing film; and a transport unit transportingthe work-piece at least between the grinding unit and the polishing unitand positioning the work-piece in the grinding unit and the polishingunit.
 25. The processing apparatus as claimed in claim 24, wherein saidgrinding unit includes a grindstone having abrasive grains whichgenerate mechano-chemical reaction with respect to a processing surfaceof the work-piece.
 26. The processing apparatus as claimed in claim 25,wherein the abrasive grains have a primary average grain size of 0.8 nmto 10 μm.
 27. The processing apparatus as claimed in claim 24, whereinsaid polishing unit includes a polishing film having abrasive grainswhich generate mechano-chemical reaction with respect to a processingsurface of the work-piece.
 28. The processing apparatus as claimed inclaim 27, wherein said polishing film is flexible.
 29. The processingapparatus as claimed in claim 27, wherein the abrasive grains have aprimary average grain size of 0.8 nm to 10 μm.
 30. The processingapparatus as claimed in claim 24, wherein said grinding unit and saidpolishing unit respectively carry out a dry grinding process and a drypolishing process.